Although alpha-synuclein is highly expressed in neuronal synapses, the functional role of this protein remains unclear. Elucidating the physiological function of alpha-synuclein is important as this protein is implicated as a causative factor in familial Parkinson disease (PD), primarily because of its association with Lewy bodies, a pathological marker of PD. In cell lines transfected with either mutant alpha- synuclein or wildtype alpha-synuclein, wildtype but not mutant alpha- synuclein associate with lipid droplets, suggesting that the native protein may be involved in lipid trafficking or metabolism. In a parallel set of studies using alpha-synuclein gene-abated mice, there was a large decrease in the steady-state mass of a number of different phospholipids in both whole brain and isolated synaptosomes compared to control mice. Further, there was a significant decrease in the amount of docosahexaenoic acid in a number of different phospholipid classes, suggesting a decrease in uptake and trafficking of docosahexaenoic acid. These data suggest a down-regulation of neuronal lipid metabolism. Because fatty acid binding proteins can alter phospholipid metabolism and alter phospholipid acyl chain composition, I submit the following hypothesis: alpha-Synuclein directly affects fatty acid uptake and targeting in neurons, essentially functioning as a neuronal fatty acid binding protein. However, this hypothesis that alpha-synuclein has a role in neuronal lipid uptake, trafficking, and metabolism needs to be further elucidated using a combination of whole animal and cell culture studies. The following specific aims are designed to address the potential role of alpha-synuclein in brain lipid metabolism using alpha- synuclein gene abated mice, neuronal cultures derived from these mice, and stably transfected H293 cells expressing mutant and wildtype alpha-synuclein. These aims are: 1. Determine the effect of alpha-synuclein on the uptake and subsequent metabolism of [3H]-palmitic, [3H]-arachidonic, and [3H]- docosahexaenoic acid in brains of control and alpha-synuclein gene- abated mice in vivo using steady-state tracer kinetic analysis. 2. Using cells derived from control and gene-abated mice as well as stably transfected cell lines, determine the effect of alpha-synuclein on cellular fatty acid uptake, metabolism, and trafficking.